Intravenous catheters are generally utilized to slowly introduce fluids into the body. Occasionally, however, such catheters are required to rapidly introduce a large amount of fluid into the body. If, for example, a patient is hypovolemic and in shock or at risk of shock, the catheter is inserted into a patient's blood vessel and a large volume of fluid is rapidly delivered through the catheter.
In order to facilitate rapid, high-volume infusion of fluid into a blood vessel, the catheter should have an outside diameter equal to the maximum inside diameter of the blood vessel. However, such a catheter is obviously difficult to insert into the blood vessel. Furthermore, since a hypovolemic patient's blood vessels are often collapsed, it is often necessary to expand the blood vessel prior to the infusion of fluids.
Intravenous catheters are known which utilize a helically braided tube that inherently expands within the blood vessel after insertion. The tube is designed so that, in its natural state, its diameter is maximized by plastic memory order to use such known catheters, a sheath is telescoped thereover to condition the tube for insertion into a blood vessel. The radially constrained tube and its restraining sheath are inserted into the blood vessel. The sheath is then drawn from the blood vessel allowing the tube to expand to its natural state thereby expanding the blood vessel by exerting a radially outward bias on the walls thereof.
One problem with such known catheters is that the diameter thereof cannot be reduced after removal of the sheath. Thus, the catheter must be removed from the blood vessel while in the expanded state in which it exerts a bias upon the walls of the blood vessel. Removal of such known catheters has been known to abraid the walls of the blood vessel, encouraging subsequent blood clot formation.